Problem: Simplify the expression. $(3z^{4}-z^{3})(4z^{4}+6z^{2})$
First use the distributive property. $ 3 z^4 (4 z^4) + 3 z^4 (6 z^2) - z^3 (4 z^4) - z^3 (6 z^2) $ Simplify. $12z^{8}-4z^{7}+18z^{6}-6z^{5}$